Does anyone have the dimensions of the 458 Lott (factory chanbering) free bore set up.

Or is the factory chambering the same as a 458 Winchester that has been rechambered?

No freebore setup.

quote:

Originally posted by Mike McGuire:
Does anyone have the dimensions of the 458 Lott (factory chanbering) free bore set up.

Or is the factory chambering the same as a 458 Winchester that has been rechambered?

Mike the latest from CIP, 2002:

It is the same long and wide funnel throat as with the .458 WinMag.
No parallel-sided freebore.
The bullet has about a 1.1" run from case mouth to fully engaging the rifling.
It is just a long and wide-based "leade-only throat," considerably sloppier than the old traditional leade-only throats of the Nitro Expresses and such, which start off just a few thou bigger than bullet diameter at case mouth.

See the CIP chamber specs.
Both are listed there, same throat, starting at 2.5" for the WinMag and 2.8" for the Lott, therefore 0.300" farther out in the Lott, of course. It is not just cutting room for the Lott brass into the former WinMag throat.

Only two dimensions are needed to describe the throat fully, exactly the same for both WinMag and Lott:

1. 0.4693" (11.91 mm) wide just above the case mouth, right where the 45-degree taper down from neck diameter ends. BTW, end of neck chamber diameter is 0.4831" (12.27 mm).

2. 0-degree 29' 30" leade angle.

Wide and long, leade-only, sloppy funnel throat.


That is a good thing for keeping the pressures down in both the .458 WinMag and the .458 Lott.

It is the caveman version of a Weatherby throat.
Ol' Roy was so refined!

Ol' Roy: A Walmart brand dogfood.

Thanks Ron.

Mike, I think one of the problems Jack Lott described with the 458Win Mag was the significant amount of freebore Winchester included with their chambering. This has been discussed by Finn Aagaard too, in .458's chambered with and without freebore, with signficant velocity differences for no freebore. Maybe Winchester goofed with the freebore in the .458 and Jack Lott recognised this?

Mike,

The 458 LOTT freebore is not the same as the 458 Winchester Magnum freebore.

Per SAAMI specs, the 458 LOTT has a straight portion of .178" then a 2 degree angle of.129" to the bore diameter while the 458 WM has a long taper of 0 degrees, 29' 30". They both have a 45 degree chamfer at the case mouth to help feeding.

Headache

quote:

Originally posted by Headache:
Mike,

The 458 LOTT freebore is not the same as the 458 Winchester Magnum freebore.

Per SAAMI specs, the 458 LOTT has a straight portion of .178" then a 2 degree angle of.129" to the bore diameter while the 458 WM has a long taper of 0 degrees, 29' 30". They both have a 45 degree chamfer at the case mouth to help feeding.

Headache

So the 458 Lott is about .31 to the rifling, much shorter than the 458 Winchester.

The reason for the question relates to using reduced loads with lighter bullets such as 300-350 grains. The very long free bore in the 458 Winchester frequently causes hang fires. No problem with shotgun flake type powders but with normal rifle type powders.

quote:

The very long free bore in the 458 Winchester frequently causes hang fires.

???????

Headache:
You have left out the diameter of the parallel-sided freebore of the SAAMI throat for .458 Lott.
Please don't be such a tease. IRP!

So ... CIP and SAAMI specs differ on the .458 Lott, not a surprise.

SAAMI spec for the .458 WinMag is the same as the CIP spec. Surprise!
No more difference than in the .0001 column caused by converting mm to inches.
Agree to .001".

I do not have the SAAMI specs for .458 Lott.
The CIP specs of 2002 are exactly alike for the .458 WinMag and .458 Lott throats, as I have specified above.

I do have some old reamer drawings from the Jack Lott era.

Pre-standardization, the .458 Lott sometimes had a parallel-sided freebore of only .459" diameter that was about 0.450" long and tapered by a 1.5 degree leade over the last .3" of throat, for a total throat that was about .75" long.

That is a model of throating, Weatherby-esque, and should be copied by all.
Sort of like a scaled-up .375 Weatherby throat of 2001 spec.

quote:

Originally posted by Will:

quote:

The very long free bore in the 458 Winchester frequently causes hang fires.

???????

Read the full post. It is with reduced loads and light bullets using rifle type powders as opposed to flake shotgun powders.

RIP,

Sorry about that. The diameter of the freebore is .459". This is the min dimension. As with all SAAMI chambers it has a +.002" tolerance.

Headache

With about .31" to the rifling that would mean bullets like the 400 grain Speer could be seated to be right next to the rifling. Might be good for cast bullets as well.

RIP

Would European rifles like the CZ for example or Sauer have the CIP chamber and the 458 Winchester long run to the rifling?

Mike,
I don't know.
Some of the CZ .458 Lotts are simply .458 WinMags with the long throat, and rechambered with a .458 Lott reamer.
Not the best way to do it.
Could leave a faint (imperceptible?) chamber ring/step at the 2.5" length on the 2.8" chamber.

Surely Ruger .458 Lott rifles are SAAMI throated. Ruger is a member of SAAMI, afterall.

Headache,
Thanks for that throat diameter.
I have the 1992 SAAMI cartridge and chamber drawings, snaggable from the SAAMI web site,
but how does one get the latest?
I think the .458 Lott was not SAAMI until 2002?
Lots of new cartridges since 1992 ...

quote:

Originally posted by RIP:

Surely Ruger .458 Lott rifles are SAAMI throated. Ruger is a member of SAAMI, afterall.

Has someone got a 458 Lott Ruger and look into the chamber. There will be no need to measure to see which one it is.

quote:

Originally posted by RIP:
Ruger is a member of SAAMI, afterall.

A2 is a saami member ... that might tell you a bunch

The 458 Win Can be shot in the Lott but the Lott cannot be shot in the 458 Win. Its to long
I think that is the problem
In other words The lotts freebore is Deaper. How much deaper I don't Know.

quote:

Originally posted by jeffeosso:
Ruger is a member of SAAMI, afterall.

A2 is a saami member ... that might tell you a bunch[/QUOTE]

So Jeffe is it reasonable to assume that a 458 Lott made by Ruger, Wby etc will have SAAMI specifications.

RIP,

The 458 LOTT was issued in 1998. Any of the SAAMI members should be using the SAAMI dimensions in their rifles.

You can try calling SAAMI and ask them how to get the 458 LOTT specifications. As a consultant for SAAMI I can not give out the drawings because they are copyright protected.

Headache

Headache,
Why you SAAMI Consultant, you!
I don't want just the .458 Lott specs, I want them ALL!

Thanks for the SAAMI date on the .458 Lott. 1998.

Seems queer that CIP would adopt something different in 2002.
Is there no cooperation or "consultation" between SAAMI and CIP?
Can you not add that liaison to your job description?

I will start here:
http://www.saami.org/

quote:

Originally posted by Mike McGuire:
Does anyone have the dimensions of the 458 Lott (factory chanbering) free bore set up.

Or is the factory chambering the same as a 458 Winchester that has been rechambered?

Since Barnes is a SAAMI member, I assume they use SAAMI spec reamers. This might be of some help: According to official Barnes, when the 500-grain Banded Solid is given a COAL of 3.310-inch, it is .717-inch off the lands in their Wiseman .458WM test barrel. The same 500-grain Banded Solid at 3.580-inch COAL in the Lott Wiseman test barrel is only .288-inch off the lands.

That means that 3.58 minus 3.31 = .27" difference in COAL between the two cartridges.

.717" minus .288" = .429"
.429" minus .27" = .159" longer chamber for the .458 Win Mag. So the Winchester .458 has a longer chamber than the Lott. So says my gunsmith and SAAMI as well.

Bob

www.bigbores.ca

Bob - what you mean to say is that the winmag as a proportinally longer throat than the lott. Which is does have, obviously, if one sticks to SAAMI. We agree that PROPORTIONALLY the winmag has a longer throat.

We don't agree, however, that the winmag chamber reamer is 4.027 saami -- its 3.642, according to SAAMI ..
According to SAAMI, page 89 as marked on the page, 95 as displayed in my adobe, http://www.saami.org/Publications/206.pdf, the 458 winmag chamber reamer, assuming one knows headspace is 3.642.with a max oal of 3.4,

how do i explain the .717 measurement? several conditions could exist that make that happen.. but that is not my reported "Fact" and i don't pretend to be able to defend it. Though if the .717 is not a measurment error or typo, then it is obviously not a saami spec reamer that cut that chamber and throat, as saami says 3.642

ya'll have a nice day --

quote:

Originally posted by .458 Only:

Since Barnes is a SAAMI member, I assume they use SAAMI spec reamers. This might be of some help: According to official Barnes, when the 500-grain Banded Solid is given a COAL of 3.310-inch, it is .717-inch off the lands in their Wiseman .458WM test barrel. The same 500-grain Banded Solid at 3.580-inch COAL in the Lott Wiseman test barrel is only .288-inch off the lands.

That means that 3.58 minus 3.31 = .27" difference in COAL between the two cartridges.

.717" minus .288" = .429"
.429" minus .27" = .159" longer chamber for the .458 Win Mag. So the Winchester .458 has a longer chamber than the Lott. So says my gunsmith and SAAMI as well.

Bob

www.bigbores.ca

quote:

Originally posted by .458 Only:
The same 500-grain Banded Solid at 3.580-inch COAL in the Lott Wiseman test barrel is only .288-inch off the lands.

That basically matches up with Headache's numbers and others I got.

All I wanted was the distance from the case mouth to the rifling of a factory Lott and the reasons were in my post.

In other words, a 458 Lott factory chamber would allow you to seat the 400 grain Speer right next to the rifling.

As to power comparisons between the 458 Winchester and 458 Lott, to me it does not matter, my question was related to reduced loads.

This has been like extracting fucking teeth.

Bob

As a side note I have had some big differences with Jeffe but he is correct on the 458 Win Vs 458 Lott.

It is really simple. Any load put forward as a 458 Winchester load must be able to fit the 3.3" magazine.

Let me ask you a question. What is the length of 458 Winchester ammo loaded by Winchester, Remington etc and etc. Is there any 458 ammo loaded where the OAL is 3.6"

If we take what you are saying one step further then we could have a 45/70 Ruger, ream out 3 inches of rifling and seat a 3000 grain bullet and of course it could beat a 458 Win or Lott CZ in velocity because such a bullet would be resting on the base of the case with the Win/Lott/CZ

But lastly Bob, I can't see why you would be going to these extreme and if I might say, ridiculous lengths to establish something with a 458 Winchester.

You only have to telephone Roy Weatherby's young bloke Ed and what you get will do all the 458 Win/Lott with reduced loads. And in these modern times the 460 is small. Fuck me, a 505 CZ with a starting load would pass 460 energy.

But the bottom line is a 458 Winchester(and I think Jeffe said this several postings ago) with the bullet seated way out in a CZ is no longer a 458 and to make it clear for you, let me explain why.

Tomorrow CZ might change their rifles and a 458 is limited to the 3.3". This is exactly the same situation as Sierra MatchKings as game bullets. At the moment they might be the best game bullet the world has seen. But tomorrow they make them FMJs like they were in the 1970s.

In other words, Sierra can do what they like with MatchKings and give zero consideration to their game performance.

CZ and Wby can change magazine lengths etc and etc and only need to make sure a 458 Winchester they sell will accept a catridge 3.3" long. Do you agree with that???????????? Yes or No.

quote:

Originally posted by Mike McGuire:

quote:

Originally posted by Headache:
Mike,

The 458 LOTT freebore is not the same as the 458 Winchester Magnum freebore.

Per SAAMI specs, the 458 LOTT has a straight portion of .178" then a 2 degree angle of.129" to the bore diameter while the 458 WM has a long taper of 0 degrees, 29' 30". They both have a 45 degree chamfer at the case mouth to help feeding.

Headache

So the 458 Lott is about .31 to the rifling, much shorter than the 458 Winchester.

The reason for the question relates to using reduced loads with lighter bullets such as 300-350 grains. The very long free bore in the 458 Winchester frequently causes hang fires. No problem with shotgun flake type powders but with normal rifle type powders.

The hang fires in the 458 Win Mag are caused by powder compaction not free-bore! Free-bore cannot cause a hang fire. Excessive free-bore cause loss of velocity, or a yawing bullet or both, but not hang-fires. Hang-fires are caused by slow burn on the powder, usually, and always in the 458 Win Mag, byt cakeing of the powder by bullet seated deep enough to crush the powder charge.

quote:

Originally posted by MacD37:


The hang fires in the 458 Win Mag are caused by powder compaction not free-bore! Free-bore cannot cause a hang fire. Excessive free-bore cause loss of velocity, or a yawing bullet or both, but not hang-fires. Hang-fires are caused by slow burn on the powder, usually, and always in the 458 Win Mag, byt cakeing of the powder by bullet seated deep enough to crush the powder charge.

Read the post. I am referring to reduced loads with lighter bullets. Nothing to do with powder compaction.

quote:

Originally posted by Mike McGuire:

quote:

Originally posted by MacD37:


The hang fires in the 458 Win Mag are caused by powder compaction not free-bore! Free-bore cannot cause a hang fire. Excessive free-bore cause loss of velocity, or a yawing bullet or both, but not hang-fires. Hang-fires are caused by slow burn on the powder, usually, and always in the 458 Win Mag, byt cakeing of the powder by bullet seated deep enough to crush the powder charge.

Read the post. I am referring to reduced loads with lighter bullets. Nothing to do with powder compaction.

quote:

by WILL:
The very long free bore in the 458 Winchester frequently causes hang fires.


???????

It seems Will missread your post as well, judgeing from the post above!


McGuire,I read your post, and Maybe we are calling two different things by the same name! Hang fires happens inside the case because of incomplete egnition of the powder, and has absolutely nothing to do with free-bore! Free-bore is in the barrel of the rifle. The free-bore is in the rifle's chamber,ahead of the seated bullet, so the bullet has to jump a distance before it engages the rifleing. It is not inside the cartridge!

Now if you are calling the "AIRSPACE" inside the case left by a light powder load "FREE-BORE" then you are correct. However the airspace inside the case is not "FREE-BORE"! Free-bore is part of the chamber cut into the rifle's barrel.

........OR Maybe I'm misunderstanding what you mean by "HANG-FIRES"! A Hang-fire is when the primer is struck, and the cartridge takes some time to actually fire, after the primer is hit by the fireing pin. You know
"CLICK....time laps......Boom!"

MacD37

I will try and make this sinmple for you

If a 458 Winchester cartridge case is chambered in a standard 458 Winchester chamber then the distance from the mouth of the cartridge case to the rifling is very long, very long.

When reduced loads are used with light bullets in cartridge cases that have a small powder capacity in relation to the bore diameter....then ignition is best with the bullet against the rifling....or a very heavy crimp.

Since we are not going to use a heavy crimp and since the light bullet is a long way from the rifling then reduced loads with rifle type powders can and do give hangfires in the 458 Winchester. BUT, if a 458 barrel is chambered to accept the 458 Winchester cartridge case and where the distance from the case mouth to the rifling is very small......no hangfires with light bullets and reduced loads of rifle powders.

By "rifle type" powders I am distinguishing from shotgun flake type powders.

PS. By hangfire I mean...click...bang

quote:

Originally posted by Mike McGuire:
MacD37

I will try and make this sinmple for you

If a 458 Winchester cartridge case is chambered in a standard 458 Winchester chamber then the distance from the mouth of the cartridge case to the rifling is very long, very long.

When reduced loads are used with light bullets in cartridge cases that have a small powder capacity in relation to the bore diameter....then ignition is best with the bullet against the rifling....or a very heavy crimp.

Since we are not going to use a heavy crimp and since the light bullet is a long way from the rifling then reduced loads with rifle type powders can and do give hangfires in the 458 Winchester. BUT, if a 458 barrel is chambered to accept the 458 Winchester cartridge case and where the distance from the case mouth to the rifling is very small......no hangfires with light bullets and reduced loads of rifle powders.

By "rifle type" powders I am distinguishing from shotgun flake type powders.

PS. By hangfire I mean...click...bang

McGuire what you are discribing is a squib load not a hang fire, a hang fire happens before the bullet even moves, and free-bore in the rifle has nothing to do with that till the bullet moves!

I think we are in a debate over what things are called in OZ, and the USA, nothing more!

I have acquired a copy of Dave Kiff's
The Gunsmiths Book Of Chamber Prints
Pacific Tool & Gauge, Revised 7/2006

It has the SAAMI spec throat for the .458 Lott.
It has the SAAMI spec throat for the .458 Winchester Magnum.

SAAMI .458 Lott chamber throat:

Chamber diameter at case mouth = .483"
45-degree step down to freebore diameter runs 0.012" in length
parallel-sided freebore diameter = .459"
parallel-sided freebore length = .178"
distance from chamber case mouth to end of parallell-sided freebore = 0.190"
throat leade angle = 2 degrees
length of taper from .459" to .448" = 0.15749"
(So let's say 0.157" run of leade to bore/land diameter.)
"Groove Size" = 0.4585"
"Bore Size" = "0.45" (Or is it .448"?)
Total bullet travel in throat from chamber case mouth to fully engaged by lands:
0.190" + 0.157" = 0.347"

The total bullet travel from case mouth to full bearing lands with the .458 Win. Mag. (SAAMI and CIP are same)
and the CIP .458 Lott (same as CIP .458 Win. Mag.):
1.0562" (according to Dave Kiff drawing)
round to 1.056"

Quite a difference between the two .458 Lott throat lengths:

CIP = 1.056"

SAAMI = 0.347"

Which should mean a 458 Winchester load will develop more pressure and velocity if fired in a SAAMI chambered 458 Lott and will drop pressure and velocity if fired in a CIP chambered 458 Lott.

...And in the real world, there are a LOT of throats that are cut to neither of those specs so unless you have a chamber cast of your rifle (or pistol in my silly toy's case) I would suggest not making any assumptions about anything without measuring. Plenty of people cut throats separately from the reaming process and then all bets are off. I do not wish to argue the merits of the different methods of chambering a .458 Lott, I just wished to point that out.

Happy Shooting,

Mike,
I finally understand why all the .458 WinMags I ever owned could barely make 1.5 MOA for three shots when all was perfect with the gun, ammo, conditions, and shooter.

However, both 460 Wbys I have owned ...
a straight factory, Japanese Mark V "Custom Deluxe,"
and a BBK-02 with McGowen 1:12" stainless barrel in a Boyd laminate stock ...
both were 0.5 MOA when I did my part,
with 115 grains of IMR-4350 and 500-grainers.

The .458 WinMag throat (same by SAAMI or CIP) is like a shotgun with a custom forcing cone job!
Instead of a 5-degree cone, it has a 1/2-degree cone.

It is the caveman way of out-doing Weatherby freebore.
It is indeed a pressure reliever to allow the runt .458 WinMag to deliver the mail without blowing a gasket.

Enlightenment.

Ron,

My experience with 460s has only been with Mark Vs and they have all shot extremely well with the 115 grains of IMR 4350 and 500 grain Hornadys and also 115 grains of Win 760.

The most accurate one was one of a pair that were originally ordered in about 1970 with a phone call to old Roy. One of the pair sat unused until the early 1990s. I bedded and flaoted it and its accuracy was staggering. After a couple of years I sold it to an Australian gun writer called John Woods, who several years ago married an American and moved there. He did the write up of the 460 in I think the Barnes number 4 manual. That is not the first time I have seen top accuracy from a new barrel that has not be used until many years later.